This invention relates to valves, and in particular to an automatic shutoff valve for use in a swimming pool skimmer, where it is important to prevent the suction of air as a result of a low liquid level.
The instant invention utilizes the principle of buoyancy. It employs the use of a float that has sufficient buoyancy in liquid to resist the downward forces created when significant down flow is present, but cannot sustain buoyancy when immersed in a gas. In applications such as skimmer drains for swimming pools and other applications where liquid flows to the suction inlet of a liquid lubricated pump, considerable damage can result to the pump should the pump lose its prime because the flow of liquid to the pump is replaced by a flow of air or other gas. There are numerous occasions such as during periods when pool owners are on a lengthy vacation, that proper pool maintenance is not performed. During those times the summer heat frequently causes a very significant loss of water through evaporation. A leak in the pool structure, or its circulating system, can also cause a loss of water. When the water level drops below the lowest level of the skimmer opening, the residual water in the skimmer body is quickly sucked out by the pump; the pump loses its prime and becomes air bound. This causes the seals of the pump to overheat and eventually results in serious damage or even destruction of the pump. Conversely, when excessive rains occur, it is necessary to pump out the excessive water so that proper skimming of the surface can be performed by the skimmer assembly. Usually the pumping down period is quite lengthy, with only occasional checks being made on the water level. Too often an excessive amount of water is accidentally withdrawn. Unless immediately corrected, this results in the same disastrous results as previously cited. A need exists for a safety check valve that can easily be inserted into an existing skimmer suction outlet that will protect the circulating pump from damaging situations such as those previously mentioned.
The design of a typical swimming pool, skimmer assembly, and circulating system is depicted in prior art FIG. 1 and FIG. 2. Pool 9 is filled with water 10 and communicates with pump 12 through skimmer assembly 11, comprising a basket strainer 11a and an unprotected skimmer outlet pipe 11b. A second means of communication between water 10 and pump 12 is through main drain 14, main drain outlet pipe 16 connecting with skimmer outlet pipe 11b and then to pump 12. The discharge of pump 12 typically flows through filter 13 and is returned to pool 9 through pool inflow pipe 17. When pump 12 is not circulating water through the system, the water levels in pool 9 and skimmer assembly 11 are equalized by gravity flow through the circulating system.
The use of check valves to stop the flow of liquids is well known. U.S. Pat. No. 999,619 to J. M. Young, and U.S. Pat. No. 1,538,656 to G. E. Richardson, both describe ball check valves that are designed to operate in the normally closed position, and must be opened manually by means of a ball-lifting device, so that temporary flow is permitted. They then re-close and remain closed when water is present above the valve seat. U.S. Pat. No. 4,240,167 to Elbert G. Gilliland describes a flapper type check valve that also is designed to operate in the normally closed position, and must be opened manually by a lifting device, to permit temporary flow. It then re-closes and remains closed when water is present above the valve seat.
U.S. Pat. No. 4,700,741 to Murphy provides a spring- loaded ball check valve that operates in the open position when there is flow through the valve acting against the spring-loaded ball, but closes when flow ceases or attempts to change direction. U.S. Pat. No 4,687,023 to Harbison et al. describes a freely reciprocating ball check valve that is not spring loaded but requires a reversal of the direction of flow to move the ball to the sealing seat. The ball check is not buoyant, and cannot differentiate between liquid and gas.
The instant invention operates contrary to the typical prior art check valves, in that it is designed to operate in the normally open position when immersed in liquid. It also has the ability to discern the difference between the flow of liquid versus the flow of gases. The float is buoyant in a liquid but is not buoyant in a gas. It therefore has the ability to remain in the closed position until a liquid level above and below the valve is restored. The design of the instant invention does not require the use of a guide rod(s) that would project above the top of the retainer. Such protrusions would seriously limit, or prevent, the valve from fitting within the confines of most intended applications, where a strainer basket is located a short distance above the suction outlet. The float of the preferred embodiment is constructed of celluloid or similar plastic and of the same dimensions typical of ping-pong balls. It can in fact be a ping-pong ball. Its thin wall, high strength, and light weight design provide superior buoyancy and resistance to deformation. The superior buoyancy of the float create its ability to release itself from the valve seat, unless a significant negative pressure exists below the seated float as would be created by a suction pump. The design therefore does not require the use of any float lifting devices as commonly required in toilet tank type check valve assemblies. The instant invention does not utilize a spring and does not require a change of direction to the flow through the valve to cause it to close.
It is the objective of the present invention to provide an automatic shutoff valve which is self contained, simple, economical and has been designed to fit the common configurations of swimming pool skimmer drain assemblies with little or no modification. The automatic shutoff valve closes safely without the need to stop the circulating pump, which in typical installations, is also connected to the bottom drain of the pool. The bottom drain portion of the circulating system will continue to supply adequate water to maintain normal operation of the pump without damaging it. An advantage of the present invention is its ability to automatically restore the system to normal operation unattended, in the event normal rainfall restores the water level in the pool to a safe operating level, or if water is added by an attendant. Since pool circulating pumps are normally programmed to operate for less than twenty-four hours per day, the normal temporary shut down will restore the valve to its normal open position if sufficient rainfall has occurred, or if water has been added by a refill device. When water has been added to the pool manually, the attendant need only stop the pump momentarily to release the float from the outlet of the valve and immediately restore normal operation.